U.S. patent number 4,723,460 [Application Number 07/008,151] was granted by the patent office on 1988-02-09 for robot wrist actuator.
Invention is credited to Mark E. Rosheim.
United States Patent |
4,723,460 |
Rosheim |
February 9, 1988 |
Robot wrist actuator
Abstract
A robot wrist actuator includes a mechanical joint having a
forward and a rearward bearing assembly. The bearing assemblies
rotate about respective spaced-apart center points positioned along
a primary axis. Each bearing assembly includes an outer and an
inner bearing. The outer and the inner bearings pivot about
respective axes that are substantially perpendicular to each other
and intersect at the respective center point. First and second
linkage assemblies for transmitting motion from the rearward
bearing assembly to the forward bearing assembly are rotatably
secured to a housing. The first linkage assembly is attached to the
forward outer bearing at one end and to the rearward outer bearing
at another end. The second linkage assembly is attached to the
forward inner bearing at one end and to the rearward inner bearing
at the other end. A drive assembly provides motive force to the
rearward bearing assembly. A tool member adapted for tool
attachment is attached to the forward outer bearing. Pivotal
movement of the rearward bearings about their respective axes
caused by the drive assembly is transmitted through the first and
second linkage assemblies to the forward assembly so that the tool
member is movable in a hemispherical operating range. In addition,
the housing is preferably rotatable along the primary axis so that
the tool member is movable to any position along a hemispherical
operating range in an efficient manner.
Inventors: |
Rosheim; Mark E. (St. Paul,
MN) |
Family
ID: |
26677870 |
Appl.
No.: |
07/008,151 |
Filed: |
January 22, 1987 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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600016 |
Apr 12, 1984 |
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Current U.S.
Class: |
74/490.06;
403/58; 901/22; 901/25; 901/28; 901/29 |
Current CPC
Class: |
B25J
17/0275 (20130101); B25J 17/0283 (20130101); Y10T
74/20335 (20150115); Y10T 403/32049 (20150115) |
Current International
Class: |
B25J
17/02 (20060101); B25J 017/00 () |
Field of
Search: |
;414/735,730,4,2,1
;901/27-29,25,22,15 ;403/58,57 ;74/479,98 ;248/179,184,284
;33/321 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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9447 |
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Apr 1980 |
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EP |
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2752236 |
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Jul 1980 |
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DE |
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3036116 |
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May 1982 |
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DE |
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Other References
"Robot Wrist Actuators," Robotics Age, Nov./Dec. 1982, pp. 15-22.
.
"Pictorial Handbook of Technical Devices," by Pete Grafstein &
O. Schwarz, published by the Chemical Publishing Company, Inc. of
New York, pp. 16-17, 1971..
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Primary Examiner: Spar; Robert J.
Assistant Examiner: Underwood; Donald W.
Attorney, Agent or Firm: Kinney & Lange
Parent Case Text
This is a continuation of Ser. No. 600,016, filed Apr. 12, 1984,
now abandoned.
Claims
What is claimed is:
1. A mechanical joint comprising:
a support structure with a primary axis;
a forward and a rearward bearing assembly spaced from each other,
each assembly having an inner and outer bearing means, each bearing
means having an outer race member, an inner race member, and a
bearing section disposed therebetween, and each bearing assembly
being positioned about a centerpoint disposed on the primary axis,
the outer race of the outer bearing means being pivotally attached
to the housing, the inner race member of the outer bearing means
being pivotally attached to the outer race member of the inner
bearing means, and the inner race member of the inner bearing means
being pivotally secured to the housing;
first linkage means for transmitting pivotal movement from the
rearward outer bearing means to the forward outer bearing means and
second linkage means for transmitting pivotal movement from the
rearward inner bearing means to the forward inner bearing menas,
each linkage means secured to the support structure and rigidly
attached to the respective bearing means so that pivotal movement
is transmitted by the linkage means;
drive means for effecting selective movement of the rearward inner
and outer bearing means such that the movement is transmitted by
the first and second linkage means to the forward inner and outer
bearing means; and
an implement member adapted for securing an implement thereto, said
implement member being attached to the forward bearing assembly so
that movement of the implement member is effected in a generally
hemispherical operating range.
2. The joint of claim 1 wherein the driving means includes first
and second spaced-apart push/pull rods, each push/pull rod
independently acting on the support structure and having at least
one universal joint, and a drive shaft disposed along the primary
axis and attached to the inner ring of the rearward outer bearing
such that pivotal movement is imparted to the inner and outer
bearing means of the rearward bearing assembly.
3. The joint of claim 2 wherein the push/pull rods are spaced from
each other approximately 90.degree..
4. The joint of claim 2 wherein each push/pull rod is independently
actuated by a hydraulic cylinder.
5. The joint of claim 1 and further including a collar rotatably
attached to the support structure and wherein the drive means
includes means for holding the collar in a stationary angular
position fixedly attached to the collar and a drive shaft secured
to the rearward bearing assembly for rotating the support structure
within the collar.
6. The joint of claim 5 wherein the means for holding the collar
include first and second spaced-apart push/pull rods.
7. The joint of claim 5 wherein the drive shaft is disposed along
the primary axis.
8. The joint of claim 1 wherein the drive means includes:
a triordinate drive shaft assembly having a first inner drive shaft
member rotatable about the primary axis cooperating with the
rearward bearing assembly so that pivotal movement is imparted to
the inner bearing assembly, a second drive shaft member attached to
the rearward bearing assembly for holding the support structure in
a fixed angular position, and a third drive shaft member rotatable
about the primary axis; and
a pivot arm having first and second ends with the first end
pivotally attached to the third drive shaft member and the second
end pivotally secured to the support structure such that when the
third drive shaft member is rotated, pivotal movement is imparted
to the outer bearing means of the rearward bearing assembly.
9. The joint of claim 8 wherein the first and second ends of the
pivot arm are disposed approximately 90.degree. apart with respect
to the primary axis.
10. The joint of claim 1 wherein the first and second linkage means
are each non-parallel equal crank linkage assemblies.
11. The joint of claim 10 wherein the first linkage assembly
includes a forward pivot pin in rotatable cooperation with the
support structure and being fixedly attached at one end to the
first linkage assembly and fixedly attached at another end to the
outer race member of the forward outer bearing means and including
a rearward pivot pin in rotatable cooperation with the support
structure and being fixedly attached at a first end to the linkage
assembly and fixedly attached at a second end to the outer race
member of the rearward outer bearing means.
12. The joint of claim 10 wherein the second linkage assembly
includes a forward pivot pin in rotatable cooperation with the
support structure and being fixedly attached at one end to the
second linkage assembly and fixedly attached at another end to the
inner race member of the forward inner bearing means and including
a rearward pivot pin in rotatable cooperation with the support
structure and being fixedly attached at one end to the second
linkage assembly and fixedly attached at another end to the inner
race member of the rearward inner bearing means.
13. The joint of claim 1 wherein the first and second linkage means
each include a forward spur gear and a rearward spur gear in
cooperation with each other, each spur gear fixedly attached to a
pivot pin that is in rotatable cooperation with the support
structure and is fixedly attached at another end to the respective
bearing means for transmitting pivotal movement from the respective
bearing means of rearward bearing assembly to the respective
bearing means of the forward bearing assembly.
14. The joint of claim 1 and further including a fluid passage
comprising a first fluid passage section through the drive shaft, a
second fluid passage section disposed within the inner race member
of the rearward outer bearing means, a third fluid passage section
disposed within the bearing section and the inner and outer race
members of the outer bearing means, a fourth fluid passage section
disposed within the outer race member, a rearward rotary union
assembly rotatably attaching the rearward outer bearing means to
the support structure and having a fifth fluid passage section, a
sixth fluid passage section located within the support structure, a
forward rotary union assembly having a seventh fluid passage
section and rotatably attaching the forward outer bearing means to
the support structure, an eighth fluid passage section disposed
within the outer race member of the forward outer bearing means, a
ninth fluid passage section disposed within the bearing section and
the inner and outer race members of the forward outer bearing
means, a tenth fluid passage section disposed within the inner race
member of the forward outer bearing means and an eleventh fluid
passage section disposed within the implement member, all of the
fluid passage sections in fluid communication to form the fluid
passage.
15. A bearing assembly for use in a mechanical joint having means
for delivering motive force to a tool member, the assembly
comprising:
first and second means for transmitting motive force;
an inner and an outer bearing means disposed about a common
rotational centerpoint that each bearing means is rotatable about,
each bearing means having an outer race member, an inner race
member and a bearing section disposed therebetween, the assembly
being disposed in a support structure with the inner race member of
the outer bearing means being pivotally attached to the outer race
member of the inner bearing means, and the inner race member of the
inner bearing means and the outer race member of the outer bearing
means each being pivotally attached to the support structure;
and
wherein the first and second means for transmitting motive force
are operatively attached to the inner bearing means and the outer
bearing means, respectively, in pivotal relationship with the
support structure such that motive force is transmitted through the
bearing assembly to the means for delivering motive force to a tool
member.
16. The assembly of claim 15 wherein the outer and inner bearing
means pivot about first and second pivot axes defined by first and
second sets of pivot pins, respectively, said pivot axes disposed
substantially perpendicularly to each other.
17. The assembly of claim 16 wherein the first set of pivot pins is
rotatably secured to the support structure and fixedly attached to
the outer race member of the outer bearing means.
18. The assembly of claim 16 wherein the second set of pivot pins
is rotatably secured to the support structure and fixedly attached
to the inner race member of the inner bearing means.
19. A wrist construction comprising:
a support structure;
means for delivering motive force to a tool member; a first
assembly having a first member and a second member and the first
member pivotally attached to the support structure and the first
and second members being retained about a first centerpoint during
movement of the first and second members and the first and second
members being movable about the first centerpoint;
a second assembly having a third member and a fourth member and the
third member being pivotally attached to the support structure and
the third and fourth member being retained about a centerpoint
during movement of the third and fourth members and the third and
fourth members being movable about the second centerpoint;
first linkage means for transmitting pivotal movement from the
first member to the third member and second linkage means for
transmitting pivotal movement from the second member to the fourth
member with the first and second linkage means being attached to
the first and second members and third and fourth members,
respectively, such that the respective linkage means transmits
movement between the respective members; and
wherein the first and second center points are disposed along a
common axis and wherein the means for delivering motive force to a
tool member is operatively connected to the first assembly such
that movement is transmitted from the second to the first assembly
and to the means for delivering motive force.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention relates to mechanical joints and robot
wrists, and in particular, it relates to robot wrists having a
displacement capability throughout a hemispherical operating
range.
2. Description of the Prior Art.
Interest in robotics and the use of robots in industrial
applications has greatly increased in recent years. One area in
which the use of robots has become important is the replacement of
humans in tasks that involve manual work, such as welding, material
handling, paint spraying, and assembly. Many of these tasks require
working in cramped spaces or performing complex maneuvers. To
perform such tasks, a robot arm or wrist should be able to
rotationally move in a range similar to a human wrist and at a
dwell time acceptable for the particular task involved.
One article reviewing the development of robot arms and wrists is
entitled, "Robot Wrist Actuators," Robotics Age, November/December
1982, pp. 15-22, and was written by the applicant of the present
application. In the article, several characteristics are described
that make robot wrists attractive. One characteristic is that a
mechanical arm or wrist can be safely used in areas where there is
a danger of explosion if the wrist is driven by hydraulic
actuators. However, there are several disadvantages with the prior
art robot arms and wrists. Some of the disadvantages are also
enumerated in the above-mentioned article and include large and
bulky mechanical joints, slow dwell time in some rotational
directions and low mechanical efficiency.
A number of well known universal joints are illustrated and
described on pages 16 and 17 of the Pictorial Handbook of Technical
Devices by Pete Grafstein and O. Schwarz, published by the Chemical
Publishing Company, Inc. of N.Y., 1971. Although rotational motion
can be transmitted through the universal joints illustrated on
pages 16 and 17, the universal joints cannot be used in operations
for transmitting pitch, yaw and roll motion to an implement or tool
member.
A rotary actuator mechanism is described in the Higuchi et al U.S.
Pat. No. 4,009,644. However, the rotary actuator of the Higuchi et
al Patent is not very useful for the transmission of pitch, yaw and
roll motion to a tool or implement member.
A number of robot joints are illustrated in the Vykukal U.S. Pat.
No. 3,405,406 and the Vykukal et al U.S. Pat. No. 4,046,262. The
Vykukal patents decribe hard-type space suits that permit the user
inside the space suit to move around somewhat unrestricted.
The Bolner U.S. Pat. No. 3,912,172 describes a back-drivable,
direct drive, hydraulically-actuated pitch and roll actuator.
The Rosheim U.S. Pat. Nos. 4,194,437 and 4,296,681, which were
issued to the applicant of the present application, describe
hydraulic servomechanisms which impart rotary movements to a device
to be driven.
The Stackhouse U.S. Pat. No. 4,068,536 describes a remotely-driven,
mechanical manipulator. The manipulator is controlled by three
concentric drive shafts which terminate in a spherically-spaced
wrist mechanism.
The Totsuka U.S. Pat. No. 3,739,923 and the Niitu et al U.S. Pat.
No. 3,784,031 describe a manipulator arm having two parallel
rotating drive shafts in a beveled gear system which translates the
drive shaft's rotating motion to a bending pitch motion and rotary
roll motion in a tool member.
A mechanical wrist is described in German Pat. No. 2,752,236 that
includes three eletric motors, providing pitch, yaw, and roll,
which are mounted on the outside of a housing with the inside of
the housing being hollow. The wrist is used for holding welding
tongs and the hollow inside housing permits electrical power lines
to be fed through the wrist.
The Molaug U.S. Pat. No. 4,107,948 describes a flexible robot arm
that is composed of a number of mutually connected rigid links
being connected at one end to a drive means and at the other end to
a tool member that is to be rotated. Another robot arm is
illustrated in the Wells U.S. Pat. No. 3,631,737. The robot arm of
the Wells patent includes a plurality of rigid tubular sections
joined end-to-end by flexible joints to form an articulated arm.
The rigid sections are manipulated by slender control cables which
are attached to the respective sections and selectively extend and
retract.
SUMMARY OF THE INVENTION
The present invention includes a robot wrist actuator having a
mechanical joint mounted within a support frame. The mechanical
joint includes forward and rearward bearing assemblies. Each
assembly is concentrically positioned about respective spaced-apart
forward and rearward center points that lie along a primary axis
running longitudinally through the housing. Each bearing assembly
includes an outer and an inner bearing that are disposed around the
respective forward and rearward center points. The outer bearing
and the inner bearing are each rotatable about individual rotation
axes and are pivotally secured to the housing about individual
pivot axes that are perpendicularly disposed with respect to each
other and intersect at the respective forward and rearward center
points. The inner bearing is secured to the outer bearing so that
when the inner bearing is rotated, the outer bearing pivots about
its pivot axis about its rotation axis. Similarly, when the outer
bearing is rotated about its rotation axis, the inner bearing
pivots about its pivot axis.
First and second linkage assemblies transmit pivotal movement of
the rearward bearing assembly to the forward bearing assembly. The
first linkage assembly is attached at one end to the forward outer
bearing and attached at another end to the rearward outer bearing
transmitting pivotal movement of the rearward outer bearing to the
forward outer bearing. The second linkage assembly is attached at
one end to the forward inner bearing and attached at another end to
the rearward inner bearing transmitting pivotal movement of the
rearward inner bearing to the forward inner bearing.
A drive assembly provides motive force for pivoting the inner and
outer bearings of the rearward bearing assembly. A tool member
adapted for tool attachment is attached to the forward outer
bearing.
Compound rotational motion of the forward bearing assembly and tool
member is caused by the drive assembly pivoting both the rearward
outer and inner bearings resulting in the first and second linkage
assemblies transmitting the same motion to the forward inner and
outer bearings so that the tool member is movable in a
hemispherical operating range. In an alternative embodiment, the
housing is also rotatable along the primary axis so that the tool
member is movable along the hemispherical operating range.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the apparatus of the present
invention with portions broken away so that the bearing assemblies
are more clearly illustrated;
FIG. 2 is a sectional view illustrating the outer bearings and a
linkage assembly connecting the two with portions shown whole for
purposes of clarity;
FIG. 3 is a sectional view illustrating the inner bearings and the
linkage assembly connecting the inner bearings with portions shown
whole for purposes of clarity;
FIG. 4 is a perspective view of the apparatus illustrating its
operation using hydraulic cylinders;
FIG. 5 is a perspective view showing the apparatus in a yaw
movement from a primary axis with portions shown whole for purposes
of clarity;
FIG. 6 is a perspective view of the apparatus illustrating pitch
movement from the primary illustrating pitch movement from the
primary axis with portions shown whole for purposes of clarity;
FIG. 7 is a perspective view illustrating an alternative embodiment
of the linkage assembly;
FIG. 8 is a perspective view of an alternative embodiment of a
drive mechanism of the drive mechanism of FIG. 8; and
FIGS. 9 and 10 are sectional views of the drive mechanism of FIG.
8; and
FIGS. 11 and 12 are sectional views of an alternative embodiment
having a fluid passage.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The robot wrist actuator of the present invention is generally
indicated at 20 in FIG. 1. Throughout the figures, like reference
characters will be used to indicate like elements. The robot wrist
actuator includes a forward bearing assembly 22 and a rearward
bearing assembly 24 disposed preferably within a housing 26. The
housing 26 is preferably a cylindrical wall with a forward portion
34 and a rearward portion 36.
The forward and rearward bearing assemblies 22 and 24 rotate about
a forward center point 23 and a rearward center point 25,
respectively, as illustrated in FIG. 2. The forward and rearward
center points are spaced from each other along a primary axis 28
running substantially coaxially through the housing 26. A support
and drive shaft 30 (which is discussed subsequently) is attached to
the rearward bearing assembly 24 for providing motive force to the
present invention. An implement member 32 adapted for mounting an
implement thereon, such as a paint sprayer or welding tool, is
attached to the forward bearing assembly 22.
The forward bearing assembly 22 includes a forward outer bearing
section 38 and a forward inner bearing 40 section. Both outer and
inner bearing sections 38 and 40 are concentrically disposed about
the forward center point along the axis 28 each having a movable
axis of rotation. The inner bearing section 40 pivots about a first
forward pivot axis 44 that runs through the center point 23 and the
primary axis 28, as illustrated in FIGS. 1 and 2. The outer bearing
section 38 pivots about a second forward pivot axis 42 that runs
through the center point 23 and the primary axis 28, as illustrated
in FIGS. 1 and 3. The first and second pivot axes 44 and 42 are
disposed substantially perpendicularly to each other.
The outer bearing section 38 preferably includes a bearing 50 and
an outer ring 46 press fitted onto an outer race surface of the
bearing, and an inner ring 48 also press fitted within an inner
race surface of the bearing. The rings 46 and 48 rotate freely with
respect to each other about the rotation axis of the bearing
50.
Similarly, the inner bearing section 40 has a bearing 56, an outer
ring 52 press fitted onto an outer race surface of the bearing 56,
and an inner disc 54 also press fitted within an inner race surface
of the bearing 56. The ring 52 and disc 54 are free to rotate with
respect to each other about the rotation axis of the bearing
56.
The inner bearing section 40 and the outer bearing section 38 are
pivotally attached to each other, preferably by pivot pins 47 and
49. Pivot pins 47 and 49 are rigidly secured to the outer ring 52
at one end and rotatably secured within the inner ring 48 at
another by bushings or bearings. The pins 47 and 49 are disposed
along an axis running through the center point 43. The pivotal
connection between the inner bearing section 40 and the outer
bearing section 38 permits both bearing sections to pivot about the
pivot axes 42 and 44 simultaneously. Although pins are employed to
pivotally connect the outer ring 52 with the inner ring 48, any
suitable manner of attachment is within the scope of the present
invention.
Likewise, the rearward bearing assembly 24 includes an outer
bearing section 58 and an inner bearing section 60, as illustrated
in FIG. 1, each having a movable axis of rotation. The outer
bearing section 58 pivots about a first rearward pivot axis 62
which intersects the rearward center point 25 on the primary axis
28, as illustrated in FIG. 2. The inner bearing section 60 pivots
about a second rearward pivot axis 64 that intersects the rearward
center point on the primary axis 28, as illustrated in FIG. 3.
The outer bearing section 58 includes a bearing 70, an outer ring
66 press fitted onto an outer race surface of the bearing 70, and
an inner ring 68 press fitted onto an inner race surface of the
bearing 70. The rings 66 and 68 freely rotate with respect to each
other about the rotation axis of the bearing section 58.
The inner bearing section 60 has a bearing 76, an outer ring 72
press fitted onto an outer race surface of the bearing 76, and an
inner disc 74 press fitted onto an inner race surface of the
bearing 76. The ring 72 and disc 74 freely rotate with respect to
each other about the rotation axis of the bearing section 60.
The inner bearing section 60 and the outer bearing section 58 are
pivotally attached to each other, preferably by pivot pins 71 and
73. Pivot pins 71 and 73 are rotatably attached to the outer ring
72 at one end and rotatably secured within the inner ring 68 at
another end and are disposed along an axis running through the
center point 25. The pivotal connection between inner bearing
section 60 and outer bearing section 58 permits both bearing
sections to pivot about the pivot axes 62 and 64 simultaneously.
Although pins are employed to connect the outer ring 72 with the
inner ring 68, any suitable manner of attachment is within the
scope of the invention.
The bearings 50, 56, 70 and 76 are preferably either roller or ball
bearings. Generally, roller or ball bearings include an inner race,
an outer race and a plurality of bearings disposed therebetween in
grooves. However, any suitable bearings that permit rotation of the
rings with respect to each other are within the scope of the
present invention.
A first linkage assembly 80 is rotatably secured to the housing 26,
as best illustrated in FIGS. 1 and 2. Although the assembly 80 is
illustrated as attached to the outside of the housing, the assembly
80 can be positioned within the housing as will be apparent from
the description below. The linkage assembly 80 transmits pivotal
movement from the rearward outer bearing section 58 to the forward
outer bearing section 38. For purposes of description, this pivotal
movement is commonly referred to as pitch movement. In one
preferred embodiment, the linkage assembly 80 is a non-parallel
equal crank linkage assembly that includes a forward pivoting
member 82, a rearward pivoting member 84 and a middle pivoting
member 86, pivotally connected to each other by linkage pivot pins
88 and 90. A first forward outer bearing section pivot pin 92 is
fixedly attached to the pivoting member 82 at one end and extends
through an opening 94 in the housing 26 along the pivot axis 42 and
is fixedly attached at another end to the outer ring 46 of the
bearing section 38. A second forward outer bearing section pivot
pin 96 rotatably extends through an opening 98 in the housing 26 at
an oppositely-facing location and also extends along the axis 42.
The pin 96 is fixedly attached at one end to the outer ring 46 and
is rotatably secured to the housing at another end. The outer
bearing section 38 is pivotal about the pivot axis 42 while
rotating the inner ring 48 of the outer bearing section 38 about
the pivot axis 44 of the inner bearing section 40.
Similarly, a first rearward outer bearing section pivot pin 100 is
fixedly attached to the pivoting member 84 at one end and extends
through an opening 102 in the housing 26 along the pivot axis 62
and is fixedly attached to the outer ring 66 of the bearing section
58 at another end. A second rearward outer bearing section pivot
pin 106 is rotatably secured to the housing 26 at one end and
extends along the pivot axis 62 through an opening 108 in the
housing 26 positioned at an oppositely facing location to the
opening 102. The pin 106 is fixedly attached at another end to the
outer ring 66 of the bearing section 58. The housing is rotatable
about the pivot axis 62 with respect to the outer bearing section
58.
A second linkage assembly 110 is rotatably secured to the housing
26, as best illustrated in FIGS. 1 and 3. Although the assembly 110
is illustrated as attached to the outside of the housing, the
assembly 110 can also be positioned within the housing, as will be
apparent from the description below. The linkage assembly 110
transmits pivotal movement from the rearward inner bearing section
60 to the forward inner bearing section 40. This pivotal movement
is commonly referred to as yaw movement. In the same preferred
embodiment as described above with reference to linkage assembly
80, the linkage assembly 110 is a non-parallel equal crank linkage
assembly that includes a forward pivoting member 112, a rearward
pivoting member 114 and a middle pivoting member 116, pivotally
connected to each other by pivot pins 118 and 120. A first forward
inner bearing section pivot pin 122 is fixedly attached to the
pivot member 112 at one end and extends through an opening 124 in
the housing 26 along the pivot axis 44. The pin 122 is attached at
another end to a forward slotted block bracket 126 which is
securely fastened, such as with screws, to the inner disc 54 of the
inner bearing section 40. A second forward inner bearing section
pivot pin 127 also positioned on the pivot axis 44 rotatably
extends through an opening 128 in the housing 26 positioned at an
oppositely-facing location and is attached at another end to the
slotted block bracket 126 and provides support along with the pin
122 to the inner bearing section 40 and outer bearing section 38.
The manner of support of the inner disc 54 by the slotted block 126
permits free rotation of the outer ring 52 about the rotation axis
of the inner bearing section 40 which in turn permits pivotal
movement of the outer bearing section 38 about the pivot axis
42.
A first rearward inner bearing section pivot pin 130 is fixedly
attached at one end to the rearward pivoting member 114 and
rotatably extends through an opening 132 in the housing 26 along
the pivot axis 64. The pin 130 is attached at another end to a
rearward clevis-type bracket 134. The clevis-type bracket 134 is
securely fastened, such as with screws, to the inner disc 74 of the
inner bearing section 60. A second rearward inner bearing section
pivot pin 136 is rotatably secured to the housing and extends
through an opening 138 in the housing at an oppositely-facing
location along the pivot axis 64. The pin 136 is fixedly attached
at another end to the clevis-type bracket 134. The pins 130, 136
and the clevis-type bracket 134 provide support to the inner
bearing section 60 and the outer bearing section 58. The manner of
support of the inner disc 74 by the clevis-type bracket 134 permits
free rotation of the outer ring 72 about the rotation axis of the
inner bearing section 60 which in turn permits pivotal movement of
the housing about the pivot axis 62 with respect to the outer
bearing section 58.
Referring to FIG. 2, the drive shaft 30 is fixedly attached to the
inner ring 68 of the rearward outer bearing section 58 with a drive
clevis member 140. The drive clevis member 140 retains the inner
ring 68 which permits the outer ring 66 to rotate about the outer
bearing section's rotation axis.
The implement member 32 is similarly fixedly attached to the inner
ring 48 of the forward outer bearing section 38 by an implement
clevis member 142. The clevis member 142 permits free rotation of
the inner ring 48 about the outer bearing section's rotation
axis.
A pair of bearings 148 and 149 are press-fitted onto the outer
surface of the lower portion 36 of the housing 26, as illustrated
in FIG. 1. A collar 150 with first and second inwardly-facing
shoulders 152 and 154 is press-fitted onto the bearings 148 and 149
such that the housing 26 is free to rotate with respect to the
collar 150.
The collar 150 is held in a fixed angular position with respect to
the axis 28 by first and second push/pull rods 156 and 158. The
push/pull rods 156 and 158 are each attached at one end to a
rearward surface of the collar 150 in an approximately 90.degree.
spaced-apart relationship, as best illustrated in FIG. 4. The
push/pull rods 156 and 158 each preferably have a pair of universal
joints 160, 162 and 164, 166, respectively. The push/pull rods 156
and 158 are actuated in a general direction of arrows 168 and 170
by well known double-action-type hydraulic cylinders 172 and 174,
respectively
As illustrated in FIG. 5, when the push/pull rods 156 and 158 are
actuated in the direction of arrows 157 and 159, the housing 26 is
pivoted about the center point 25 was indicated by axis 28 being
moved angularly away from drive shaft 30, as generally indicated by
arrow 180, by rotation of the rearward outer bearing section 58 and
pivoting of the rearward inner bearing section 60 about pivot axis
64. The linkage 110 transmits the movement to the forward bearing
assembly 22, pivoting the forward inner bearing section 40 which
rotates the inner ring 48 with the forward outer bearing section 38
imparting a simple yaw movement to the implement member 32, as
generally indicated by arrow 182. As will be easily understood,
simple yaw movement in an opposite direction is accomplished by
actuating push/pull rods 156 and 158 in an opposite direction to
arrows 157 and 159.
Simple pitch movement is imparted to implement member 32 by moving
one of the push/pull rods in one direction while moving the other
push/pull rod in another direction, as illustrated in FIG. 6. For
example, push/pull rod 156 is moved in a rearward direction, as
indicated by arrow 161, while push/pull rod 158 is actuated in a
forward direction as indicated by arrow 163. The housing is pivoted
about center point 25 with the rearward outer bearing section 58
pivoting about the axis 62. The pivoting of the bearing section 58
about the axis 62 actuates the linkage assembly 80 which pivots the
forward outer bearing section 38 about the pivot axis 42 imparting
simple pitch movement to the implement member 32. Pitch movement in
an opposite direction is accomplished by reversing the movement of
the push/pull rods 156 and 158.
To produce a compound pitch and yaw movement so that the implement
member 32 is moved in a hemispherical operating range, the
push/pull rods 156 and 158 are moved such that the housing 26 is
pivoted in a direction other than the directions described
previously for simple pitch and yaw movement. The pivotal
connection of the rearward inner and outer bearing sections through
pivot pins 71 and 73 and the pivotal connection of the forward
inner and outer bearing sections through pivot pins 47 and 49
permit pivotal movement between the respective inner and outer
bearing sections such that the bearing section's rotation axes are
moved. Both linkage assemblies 80 and 110 are actuated,
transmitting pivotal movement of the rearward bearing sections to
the forward bearing sections with said movement resulting in
movement of the implement 32 to any point in a hemispherical
operating range.
To effect more efficient and quicker compound pitch and yaw
movement, the housing 26 can be rotated about the primary axis 28.
The push rods 156 and 158 hold the roller 150 in a fixed angular
position while the housing is rotated by the drive shaft 30. The
drive shaft 30 is turned by a suitable drive mechanism (not shown)
in either a direction of arrow 144 or the arrow 146, as illustrated
in FIG. 1. The attachment of the clevis 140 to the inner ring 68 of
the outer bearing section 58 and the bearing section's attachment
to the housing 26 through pins 100 and 106 causes the housing to
rotate, rotating the implement member 32.
In an alternative embodiment, illustrated in FIG. 7, the linkages
80 and 110 are replaced with spur gear linkage assemblies 190 and
191. The spur gear assembly 190 transmits the same simple pitch
movement as linkage assembly 80. The spur gear assembly 190
includes a forward pitch spur gear 192 and a rearward pitch spur
gear 194. A pin 196 is fixedly attached to the spur gear 192 and
rotatably extends through the housing 26 and is fixedly attached at
another end to the outer bearing similar to pin 92 as was described
with reference to FIG. 2. Likewise, a pin 198 is fixedly attached
to the spur gear 194 and rotatably extends through the housing 26
and is fixedly attached at another end to the rearward outer
bearing section 58 similar to pin 100, as was described with
reference to FIG. 2. As is easily understood, when the push/pull
rods 156 and 158 are moved as previously described with reference
to FIG. 6, pivotal movement of the rearward bearing section 58 will
be transmitted from spur gear 194 to spur gear 192 and to the
forward outer bearing section 38 and the implement member 32.
Likewise, spur gear assembly 191 includes a forward yaw spur gear
200 and a rearward yaw spur gear 202 with the forward spur gear
being rotatably attached to the inner bearing section 40 by a pin
204 in a similar fashion as pin 122 in the embodiment illustrated
in FIG. 3. The rearward spur gear 202 is attached to the rearward
inner bearing 60 by a pin 206 in a similar fashion as pin 130 in
the embodiment illustrated in FIG. 3. As is easily understood, when
the push/pull rods are moved as was previously described with
reference to FIG. 5, pivotal movement of the rearward inner bearing
section 60 will be transmitted from spur gear 202 to spur gear 200
and to the forward inner bearing section 40 and the implement
member 32. Although the spur gear assemblies are shown positioned
on the outside of the housing, they may be positioned within the
housing for some applications
Compound pitch and yaw movement is effected through the spur gear
assemblies 190 and 191 in a like manner as was described previously
with reference to the embodiment having the linkage assemblies 80
and 110.
In a further alternative embodiment, illustrated in FIGS. 8-10,
compound pitch and yaw movement of the apparatus of the present
invention is effected by a triordinate drive shaft assembly 210 and
a connecting arm assembly 212 replacing the drive shaft 30 and the
push/pull rods 156 and 158. The triordinate drive shaft assembly
210 includes a primary rotating drive shaft 214, a rotatable
support sleeve 220 and a rotatable outer connecting arm support
sleeve 226.
The primary rotating drive shaft 214 has a first beveled gear 216
attached at an upper end thereof, as best illustrated in FIGS. 9
and 10. The outer bearing section 58a has an outer ring 66a with a
second beveled gear portion 218 adapted for cooperation with the
beveled gear 216. The outer bearing section 58a is quite similar to
the outer bearing section 58 described previously and is pivotally
mounted to the housing 26 by pivot pins 100 and 106 as previously
described with reference to FIG. 2. However, the drive shaft 214,
unlike the drive shaft 30 in the embodiment shown in FIG. 2, does
not provide rotational movement to the housing 26 but instead
imparts yaw movement by rotating the inner ring 68a of the outer
bearing section 58a in a general direction of arrow 219 thereby
pivoting the rearward bearing section about center point 25. The
linkage 110 then transmits the movement to the forward inner
bearing section 40, pivoting the bearing section 40 and imparting
simple yaw movement to the implement member 32.
The support sleeve 220 has an upper clevis portion 221 which is
fixedly attached to the inner ring 68a. When the outer sleeve 220
is rotated in a direction of arrow 144 or arrow 146, rotational
movement of the housing is effected
The connecting arm assembly 212, as best illustrated in FIG. 8,
includes. a connecting arm member 230 whose lower end is pivotally
attached to a bracket 232. The bracket 232 is fixedly attached to
an outwardly extending plate 228 which in turn is integral to the
outer sleeve 226. A pin 234 pivotally attaches the connecting arm
member 230 to the bracket 232. An upper portion of the connecting
arm 230 is pivotally attached to the housing 26. The arm 230 is
pivotally attached by a universal joint 236 which is fixedly
attached to the housing 26. The universal joint 236 includes a
first universal joint pin 238 rotatable about a pivot axis 240
(similar to previously described pivot axis 64) that is angularly
displaced approximately 90.degree. from the pivot pin 234. A second
universal pivot pin 242 rotatably extends within the first
universal joint pivot pin 238 attaching the upper portion of the
connecting arm 230 to the universal joint 236. When the outer
sleeve 226 is rotated in the direction of either arrow 144 or 146,
the housing 26 is tilted with the rearward outer bearing section
pivoting about the pivot axis 240. The pivoting movement is
transmitted through the linkage 80 to the forward outer bearing
section, effecting a pitch movement to the implement member 32.
In a further preferred embodiment generally indicated at 249 in
FIGS. 11 and 12, the apparatus of the present invention is provided
with a fluid passage generally indicated at 250 in FIG. 11. The
fluid passage 250 provides a path for the transport of air or other
fluids, gas or liquid, wherein the entire passage is defined by
elements of rigid and durable construction. Prior art fluid
passageways made of flexible material sections needed frequent
maintenance and replacement due to the continuous flexing that is
experienced from the continual movement of a robot wrist or other
similar joint. The preferred embodiment illustrated in FIGS. 11 and
12 eliminates this problem.
Referring specifically to FIG. 12, the passageway 250 delivers air
or any other desired fluid, gas or liquid, from a suitable source
entering a drive shaft channel 252 in a drive shaft 254. The
embodiment 249 is similar in construction to the embodiment 20
illustrated in FIGS. 1 through 6 and will be described only briefly
below. The drive shaft 254 is connected to a rearward bearing
assembly 256 having an outer bearing section 258 and an inner
bearing section 260. The rearward bearing sections 258 and 260
rotate about a common center point 262 disposed at the intersection
of the longitudinal axis 28 of the housing 26. The inner bearing
section 260 pivots within the housing 26 on pivot pins 264 and 266
which are disposed on the pivot axis 64, as illustrated in FIG. 12
and the outer bearing section pivots about the axis 62 on pivot pin
267 and a rotary-type union 269.
Movement from the rearward bearing assembly is transmitted to a
forward bearing assembly 268 by pitch linkage assembly 270 and yaw
linkage assembly 272, as previously described with reference to
FIGS. 1-3. The forward bearing assembly 268 also has an bearing
section 274 and an inner bearing section 276 disposed about a
common center point 278 which is positioned on the longitudinal
axis 28. The outer bearing section 274 is pivotally attached to the
housing 26 along the pivot axis 42 by a rotary-type union 280 and a
pivot pin 282. The preferred embodiment in FIGS. 11 and 12
functions in much the same way as the apparatus described with
reference to FIGS. 1-3, moving an implement member 284 in a
hemispherical operating range.
The fluid channel 252 in the drive shaft 254 is connected to a
fluid channel 286 in a clevis member 255. The clevis member 255 is
fixedly attached to an inner ring 288 of the outer bearing section
258. The clevis channel 286 is fluidly connected to a channel
section 290 of the inner ring 288 of the bearing section 258. The
outer bearing section 258 further includes spaced-apart bearings
292 and 296 in press fitting relationship with the inner ring 288
and an outer ring 294. The spaced-apart bearings 292 and 296 define
an annular channel section 300 between the inner and outer rings of
the outer bearing section 258. The channel section 300 is fluidly
connected to the channel section 290 of the inner ring 288. A
channel section 302 extends through the outer ring 294 and into a
rotatable section of the rotary union 269. The channel 302 is
fluidly connected through the rotary union to a channel section 306
disposed within the housing 26. The channel section 306 in turn is
fluidly connected to a channel section 310 by the rotary union
280.
The forward outer bearing section 274 similarly contains an outer
ring 312 and an inner ring 314 press fitted onto a pair of
spaced-apart bearings 316 and 318 to define an annular channel
section 320, as best seen in FIG. 12. The channel section 310
extends into the outer ring 312 and is fluidly connected to the
channel section 320.
The inner ring 314 includes a channel section 321 that is in fluid
communication with the channel section 320. The implement member
284 is fixedly attached by a clevis portion 322 to the inner ring
314. The clevis portion includes a channel section 324 fluidly
connected to the channel section 321 and extending through the
implement member 284 for fluid communication with a tool such as an
air powered screw driver or paint sprayer.
The embodiment in FIGS. 11 and 12 also includes a universal joint
330 manufactured by Alfred Hayd Company of West Germany. The
universal joint 330 is a precision movement-type universal
joint.
An important feature of the apparatus of the present invention is
that the apparatus is back-drivable. Since robot wrists are
generally controlled by microprocesses, the ability to program
on-line a sequence of moves has considerable advantages in time
savings and flexibility of the apparatus of the present
invention.
Although the present invention has been described with reference to
preferred embodiments, workers skilled in the art will recognize
that changes may be made in form and detail without departing from
the spirit and scope of the invention.
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